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iOS Swift 2.0 Enumerations and Optionals Introduction to Optionals Initializing Optional Values

Prateek Sanyal
PLUS
Prateek Sanyal
Courses Plus Student 2,017 Points
Posted by Prateek Sanyal
Prateek Sanyal
Courses Plus Student 2,017 Points

Why is my code failing?

It says make sure that the initializer returns a valid instance if given a valid dictionary. There are no compilation errors and everything seems to work on xcode.

optionals.swift 
struct Book {
    let title: String
    let author: String
    let price: String?
    let pubDate: String?

    init?(dict: [String: String]) {
      guard let bookPrice = dict["price"], let bookPubDate = dict["pubDate"], let bookAuthor = dict["author"], let bookTitle = dict["title"] else {
        return nil
      }

      title = bookTitle
      author = bookAuthor
      price = bookPrice
      pubDate = bookPubDate
    }
}

1 Answer

Tobias Helmrich
Tobias Helmrich
31,602 Points
Tobias Helmrich
Tobias Helmrich
31,602 Points

Hey Prateek,

you almost got it right, good job! :) However you have one problem in your code: Note that price and pubDate can be nil as they have optional types. So you shouldn't use guard for them but just for title and author because right now init also returns nil when price or pubDate are nil which shouldn't be the case. You can then assign price and pubDate after the else of guard .

Like so:

struct Book {
    let title: String
    let author: String
    let price: String?
    let pubDate: String?

    init?(dict: [String: String]) {
      guard let bookAuthor = dict["author"], let bookTitle = dict["title"] else {
        return nil
      }

      let bookPrice = dict["price"] 
      let bookPubDate = dict["pubDate"] 

      title = bookTitle
      author = bookAuthor
      price = bookPrice
      pubDate = bookPubDate
    }
}

I hope that helps! :)

Prateek Sanyal
Prateek Sanyal
Courses Plus Student 2,017 Points
Prateek Sanyal
Prateek Sanyal
Courses Plus Student 2,017 Points

Thanks buddy! I don't know why I didn't think of this.

Tobias Helmrich
Tobias Helmrich
31,602 Points
Tobias Helmrich
Tobias Helmrich
31,602 Points

No problem, glad I could help!